Typically, an engine-compressor for compressing natural gas for use as a fuel has a single cooling circuit to cool both its combustion unit and compression unit. A single cooling circuit design is not ideal because the optimal temperature for the combustion unit is higher than the compression unit of the engine-compressor. The present invention provides a dual zone cooling system to cool the combustion unit separately from the compression unit.

Most multistage compressors specify a maximum inlet pressure that may be supplied to the compressor to stay within designed limits. If the supply gas to be compressed is at a higher pressure than the specified maximum inlet pressure, then its pressure must be reduced before connecting it to the compressor. This pressure reduction is inefficient. The present invention avoids reducing the inlet pressure by routing the supply gas directly to the appropriate compression stage depending on its inlet pressure such that the compressor loads are still within the specified limits of the equipment.

Most multistage compressors specify a maximum inlet pressure that may be supplied to the compressor to stay within designed limits. If the supply gas to be compressed is at a higher pressure than the specified maximum inlet pressure, then its pressure must be reduced before connecting it to the compressor. This pressure reduction is inefficient. The present invention avoids reducing the inlet pressure by routing the supply gas directly to the appropriate compression stage depending on its inlet pressure such that the compressor loads are still within the specified limits of the equipment.

An air compressor includes a driving device and a vehicle engine. The vehicle engine includes a casing with multiple cylinders and a crank located therein. Each of the cylinders has a piston movably received therein, and each piston has a piston rod which is pivotably connected to the crank. The driving device drives the crank. A cylinder head is mounted to the casing and includes an entrance and an exit. Each of the pistons is moved back-and-forth in the cylinder corresponding thereto by rotation of the crank. Air is sucked into the cylinders via the entrance and is compressed by the pistons. The compressed air is released via the exit.

Typically, an engine-compressor for compressing natural gas for use as a fuel has a single cooling circuit to cool both its combustion unit and compression unit. A single cooling circuit design is not ideal because the optimal temperature for the combustion unit is higher than the compression unit of the engine-compressor. The present invention provides a dual zone cooling system to cool the combustion unit separately from the compression unit.

Most multistage compressors specify a maximum inlet pressure that may be supplied to the compressor to stay within designed limits. If the supply gas to be compressed is at a higher pressure than the specified maximum inlet pressure, then its pressure must be reduced before connecting it to the compressor. This pressure reduction is inefficient. The present invention avoids reducing the inlet pressure by routing the supply gas directly to the appropriate compression stage depending on its inlet pressure such that the compressor loads are still within the specified limits of the equipment.

Most multistage compressors specify a maximum inlet pressure that may be supplied to the compressor to stay within designed limits. If the supply gas to be compressed is at a higher pressure than the specified maximum inlet pressure, then its pressure must be reduced before connecting it to the compressor. This pressure reduction is inefficient. The present invention avoids reducing the inlet pressure by routing the supply gas directly to the appropriate compression stage depending on its inlet pressure such that the compressor loads are still within the specified limits of the equipment.